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If a certain sum doubles itself after 3 yrs kept at simple interest. In how many yrs will it become 5 times of its value?

  • maths -

    (1+r)^3 = 2

    2^log_2(5) = 5, so

    (1+r)^(3*log_2(5)) = 5

    3*log_2(5) = 3 * log5/log2 = 6.97 years

    Makes sense, since
    3 years = 2x
    6 years = 4x
    so, 6.97 years = 5x

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